Conventionally, those fixing heaters require a large amount of power and generate a large current fluctuation when the power is turned on or off. FIG. 1 is a general diagram showing a conventional fixing roller. A sheet of paper 3 is fed between a rotating heater roller 4 and a pressure roller 5 to heat and melt a toner image onto the paper. Heaters 1 and 2 are installed in the heater roller 4 as shown in the figure. The waveform shown in FIG. 2 is the waveform of the heater turn-on current when the ON/OFF is controlled based on temperature. P1 and P2 in the figure indicate the points of abrupt current fluctuations, which generate a fluctuation in the voltage of the supplied power and cause a flicker in a light connected to the same power supply.
FIG. 3 is a diagram showing a fluctuation in the voltage. In general, when a supplied power is viewed from the power outlet to which a power-connected device 8 (in this case, a copier) is connected, there is found low power supply impedance Rs. Therefore, the power voltage fluctuation, caused when the current consumption of the connected device 8 varies greatly and abruptly, is evaluated as the power voltage fluctuation ΔV=Rs×ΔI where ΔI is the change in the current. For example, when a light is connected to this outlet line and an abrupt voltage fluctuation occurs, the fluctuation causes a flicker in the light. It is known that the change in the current should be reduced to prevent such a flicker in the light.    Patent Document 1: Japanese Patent Laid-Open Publication No. Hei 11-95611    Patent Document 2: Japanese Patent Laid-Open Publication No. Hei 9-244466